seen on the gcc-7 branch, and now on trunk as well, with the gdc frontend merged.
https://buildd.debian.org/status/fetch.php?pkg=gcc-8&arch=alpha&ver=8-20180130-1&stamp=1517382957&raw=0 make[5]: Entering directory '/<<PKGBUILDDIR>>/build' rm -f stage_current make[5]: Leaving directory '/<<PKGBUILDDIR>>/build' Comparing stages 2 and 3 warning: gcc/cc1objplus-checksum.o differs warning: gcc/cc1obj-checksum.o differs Bootstrap comparison failure! gcc/d/lexer.o differs Makefile:24128: recipe for target 'compare' failed make[4]: *** [compare] Error 1 make[4]: Leaving directory '/<<PKGBUILDDIR>>/build' Makefile:24107: recipe for target 'stage3-bubble' failed make[3]: *** [stage3-bubble] Error 2 make[3]: Leaving directory '/<<PKGBUILDDIR>>/build' Makefile:24170: recipe for target 'bootstrap' failed make[2]: *** [bootstrap] Error 2 the object files seem to be different ones on the branch and trunk.